Run: October, 2003 - March 2005
Hands down the most frustrating cancellation event is when a bad series with tons of potential finally gets its act together on the eve of getting the axe.
Tru Calling is another doomed Jon Harmon Feldman high-minded concept that finds Eliza Dushku doing her usual tough chick shtick as a morgue attendant who dead bodies sometimes ask for help. Her day rewinds and it's up to her to prevent their death, or right some unfinished business.
It was all very procedural and boring until late season one when Jason Priestley showed up as a drifter also capable of reliving days—only he was of the belief that the dead should stay dead.
The series instantly shifted into a highly entertaining weekly cat-and-mouse dynamic with a cool metaphysical undertone and expansive mythology. It all made for a very promising second season, and the promise was delivered...for all of six episodes. (And yes, that is a pre-Hangover Zach Galifianakis doing his best to hide his face on the left. Think he answers Eliza's calls these days?)